题目

关于牛顿第二定律，正确的说法是(                ).【1】(A)物体的质量跟外力成正比，跟加速度成反比(B)加速度的方向一定与合外力的方向一致(C)物体的加速度跟物体所受的合外力成正比，跟物体的质量成反比(D)由于加速度跟合外力成正比，整块砖的重力加速度一定是半块砖重力加速度的2倍 答案：BC【1】Buses run ________ between the city and the airport.【2】The explosion _______destroyed the building.【3】Smoking in public places is not allowed, ______, throwing rubbish is also banned.【4】The water will cool the air significantly, but he explained it _________.